Stainless Steel 384 Spring
Heat-treated state
AISI/SAE 384 · UNS S38400 · JIS SUS384
Spring = spring hard
Pick spring-temper drawn wire in fine gauges for 1250 MPa tensile springs; slow work hardening means lower strength than 302 spring wire of equal diameter, at 5% elongation.
Values for the Spring condition
Other 384 tempers and conditions
384 is listed in 8 conditions; see the grade overview at 384.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault solution annealed (1010–1120 °C, rapid cool) | Default stock: solution annealed at 1010–1120 °C and rapidly cooled soft wire or bar, intended for subsequent cold heading, cold extrusion and deep drawing. | 240 | 550 | 55 | 140 HB | 2.4 % IACS |
Cold drawn | Pick lightly cold drawn bar or wire when dimensional accuracy and surface quality matter; yield rises to 380 MPa while 35% elongation still allows secondary forming. | 380 | 640 | 35 | 185 HB | 2.4 % IACS |
Quarter hard | Use quarter hard cold worked stock as the balance point: the moderate cold reduction gives 515 MPa yield yet leaves 25% elongation for limited further forming. | 515 | 760 | 25 | 18 HRC | 2.4 % IACS |
Half hard | Choose half hard cold worked material for non-magnetic fasteners and spring parts that need 690 MPa yield; formability falls to 15% elongation. | 690 | 900 | 15 | 25 HRC | 2.3 % IACS |
low-temperature stress relief after cold work (≈300–400 °C) | Apply the 300–400 °C low-temperature stress relief to cold-formed parts to cut residual stress and cracking risk while keeping essentially full strength at 700 MPa yield. | 700 | 900 | 16 | 27 HRC | 2.4 % IACS |
Three-quarter hard | Specify three-quarter hard wire, stocked only in limited quantities, for high-strength non-magnetic spring parts; 830 MPa yield comes with just 11% elongation and little forming reserve. | 830 | 1,000 | 11 | 30 HRC | 2.3 % IACS |
Full hard | Use fully cold drawn wire at maximum reduction for 930 MPa yield and 8% elongation; the low work-hardening rate keeps strength below 302/304 drawn to the same cold work. | 930 | 1,100 | 8 | 34 HRC | 2.3 % IACS |
SpringThis page Spring hard | Pick spring-temper drawn wire in fine gauges for 1250 MPa tensile springs; slow work hardening means lower strength than 302 spring wire of equal diameter, at 5% elongation. | 1,050 | 1,250 | 5 | 38 HRC | 2.3 % IACS |
What is 384 Spring?
384 Spring is 384 heat treated to Spring — pick spring-temper drawn wire in fine gauges for 1250 MPa tensile springs; slow work hardening means lower strength than 302 spring wire of equal diameter, at 5% elongation. 384 Spring has a yield strength of 1,050 MPa (152 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 5% and the elastic modulus is 193 GPa (28 Msi). 384 Spring has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,398°C (2,548 °F). Annealed is the default condition FabDigit quotes; Spring is available on request or by drawing note.
Advantages
- High strength — 1,050 MPa (152 ksi), better than 98% of stainless steel grades
Limitations
- Limited ductility — 5%, worse than 100% of stainless steel grades
- Limited service temperature — 290°C (554 °F), worse than 94% of stainless steel grades
- Limited formability — 12/100, worse than 93% of stainless steel grades
- High embodied carbon — 5.8 kg CO₂/kg, worse than 86% of stainless steel grades
- Low fracture toughness — 70 MPa·√m (63.7 ksi·√in), worse than 83% of stainless steel grades
384 Spring properties
Typical room-temperature values for 384 Spring; 23 are specific to this condition. Other listed values are 384 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
384 Spring has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,398°C (2,548 °F).
Mechanical16
384 Spring has a yield strength of 1,050 MPa (152 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 98% of stainless steel grades. Elongation at break is 5% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
384 Spring is rated for continuous service to 290°C (554 °F). It conducts heat at 16.2 W/m·K (9.36 BTU/hr·ft·°F), better than 64% of stainless steel grades. Thermal expansion is 16.5 µm/m·K (9.17 µin/in·°F).
Electrical3
384 Spring conducts electricity at 2.3 % IACS, better than 55% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (55/100), worse than 71% of stainless steel grades.
Sustainability4
Producing a kilogram of 384 Spring takes about 58 MJ of energy and emits 5.8 kg of CO₂ — more than 66% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
384 Spring's machinability is poor (32/100, worse than 62% of stainless steel grades); weldability fair (45/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 384 Spring
Is 384 easy to machine?
Tough and prone to sticking to the tool; use sharp, high-positive-rake tooling, rigid clamping, constant feed and ample coolant. Machinability is about 45 % of AISI 1212 — select dedicated non-free-machining chip-breaker geometries, or substitute 303 on parts requiring extensive turning.
Can 384 be welded?
GTAW, GMAW and resistance welding are all usable, typically with ER308L or ER347 filler. With no stabilising elements and carbon up to 0.08 %, solution treat after welding or specify low-carbon heats where intergranular corrosion resistance is required, and allow for the hot-cracking sensitivity of high-nickel weld metal.
Can 384 be formed, bent or molded?
This is the grade's main advantage: the low work-hardening rate permits high-deformation cold heading, cold extrusion, multi-station forming and deep drawing without intermediate annealing. Use phosphate or oxalate coating plus soap, or a polymer lubricant film, to prevent die pickup.
What surface finishes work on 384?
Not anodised; standard treatments are nitric or citric passivation (ASTM A967), electropolishing, mechanical polishing or barrel tumbling. It remains non-magnetic after cold working, which suits fasteners with low magnetic permeability requirements.
384 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Ccold-heading grades usually held below 0.05 | ≤ 0.08 | 0.05 |
| Mn | ≤ 2 | 1.2 |
| Si | ≤ 1 | 0.6 |
| P | ≤ 0.05 | — |
| S | ≤ 0.03 | — |
| Cr | 15 – 17 | 16 |
| Nihigh Ni stabilizes austenite, lowers work-hardening rate | 17 – 19 | 18 |
| Fe | balance | — |
384 Spring — frequently asked
What is 384 Spring used for?
384 Spring is typically used for cold-headed fasteners, rivets and cold-formed hardware. In short: best cold-heading stainless; low work-hardening austenitic; non-magnetic after cold work.
What is the yield strength of 384 Spring?
384 Spring has a typical yield strength of 1,050 MPa (152 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 98% of stainless steel grades. Strength varies by condition: see the 8 listed tempers.
Is 384 Spring easy to machine?
Not especially — machinability is rated poor (32/100, worse than 62% of stainless steel grades). Tough and prone to sticking to the tool; use sharp, high-positive-rake tooling, rigid clamping, constant feed and ample coolant. Machinability is about 45 % of AISI 1212 — select dedicated non-free-machining chip-breaker geometries, or substitute 303 on parts requiring extensive turning.
Can 384 Spring be welded?
With care — weldability is rated fair (45/100). GTAW, GMAW and resistance welding are all usable, typically with ER308L or ER347 filler. With no stabilising elements and carbon up to 0.08 %, solution treat after welding or specify low-carbon heats where intergranular corrosion resistance is required, and allow for the hot-cracking sensitivity of high-nickel weld metal.
What surface finishes work on 384 Spring?
Not anodised; standard treatments are nitric or citric passivation (ASTM A967), electropolishing, mechanical polishing or barrel tumbling. It remains non-magnetic after cold working, which suits fasteners with low magnetic permeability requirements.
Can 384 Spring be formed, bent or molded?
This is the grade's main advantage: the low work-hardening rate permits high-deformation cold heading, cold extrusion, multi-station forming and deep drawing without intermediate annealing. Use phosphate or oxalate coating plus soap, or a polymer lubricant film, to prevent die pickup.
What is the maximum service temperature of 384 Spring?
384 Spring is rated for continuous use to about 290°C (554 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 384 Annealed and 384 Spring?
Annealed is the default condition — default stock: solution annealed at 1010–1120 °C and rapidly cooled soft wire or bar, intended for subsequent cold heading, cold extrusion and deep drawing. Spring: pick spring-temper drawn wire in fine gauges for 1250 MPa tensile springs; slow work hardening means lower strength than 302 spring wire of equal diameter, at 5% elongation. Yield strength is 240 MPa in Annealed versus 1,050 MPa in Spring.
Sources
- ASTM A493 — Stainless Steel Wire and Wire Rod for Cold Heading and Cold Forging — ASTM International (2021)
- ASTM A959 — Harmonized Standard Grade Compositions for Wrought Stainless Steels — ASTM International (2022)
- ASTM A276/A484 — Stainless Steel Bars and Shapes — ASTM International (2017)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- UNS S38400 alloy data (SAE/ASTM Metals & Alloys in the Unified Numbering System) — SAE International (2017)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.